RELATIONSHIP OF CHLOROGENIC ACID CONCENTRATION IN SUNFLOWER ACHENES TO BIRD PREDATION OF SUNFLOWER

Abstract

Blackbird feeding on sunflower is a significant problem in parts of the Northern Great Plains. Therefore, experiments were initiated to determine the relationship of chlorogenic acid (CA) in sunflower achenes to bird predation and the amount of variability for CA in sunflower genotypes. Eight inbred sunflower (Helianthus annuus L.) genotypes with variable levels of resistance to blackbird (Agelaius phoeniceus L. and Xanthocephalus xanthocephalus Bonaparte) and house sparrow (Passer domesticus L.) predation were evaluated at two locations in 1979 and 1980 for seed and hull CA. Differences were observed among inbred sunflower genotypes for CA concentration in both hull and seed. However, no significant correlation between percent CA in seed and mean percent bird damage over the four tested environments was observed. An unexpected positive correlation for hull CA and bird damage was found, however. Achene samples were taken from three positions within the sunflower head (outside, middle and inside) from seven inbred lines at three sampling dates. Genotype influenced CA level in both achene components while sampling date influenced CA level in the seed only. Position of achenes within the sunflower head did not influence CA concentration of either hull or seed. Thus, it is unlikely that the CA concentration of physiologically mature sunflower achenes (hull or seed) causes the observed bird predation pattern (edge to center) on sunflower heads. CA concentration is not apparently related to bird damage.Key words: Sunflower, bird feeding, chlorogenic acid, Helianthus annus L., blackbird